The value of urea-based recirculation in screening arteriovenous fistula stenosis among end stage renal disease patients undergoing maintenance hemodialysis

There is a need for studies to establish a specific access recirculation (AR) threshold for screening arteriovenous fistula (AVF) stenosis in hemodialysis patients. This study was to assess the validity of AR against duplex doppler ultrasound in detecting AVF stenosis in hemodialysis patients. This cross-sectional study recruited chronic hemodialysis patients with AVF installment of at least three months. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), Youden’s index, and area under the curve (AUC) were calculated to establish AR thresholds for the screening of AVF stenosis<50% and AVF stenosis≥50%. The sample included 324 hemodialysis patients (193 non-stenosis, 48 stenosis<50%, and 83 stenosis≥50%). Hemodialysis patients with AVF stenosis≥50% had the highest AR (10.45±14.03%). AR was not valid in screening for AVF stenosis<50%. When screening for AVF stenosis≥50%, AR threshold of ≥4% or 5% provided optimal Youden indexes. AR threshold of 4% was found a sensitivity of 72.3%, a specificity of 46.9%, PPV of 31.9%, and NPV of 83.1%. AR threshold of 5% found a sensitivity of 60.2%, a specificity of 58.9%, PPV of 33.6%, and NPV of 81.1%. Both thresholds displayed AUC of 0.60 (95%CI 0.54–0.65, p<0.01). AR of 4% should be used for screening stenosis≥50% in hemodialysis patients.